A5050188262- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Dust and Plasma Wave Phenomena
- Laser-induced spectroscopy and plasma
- Fluid Dynamics and Turbulent Flows
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Atomic and Molecular Physics
- Fusion materials and technologies
- Electrohydrodynamics and Fluid Dynamics
- Geomagnetism and Paleomagnetism Studies
- Spectroscopy and Laser Applications
- Nuclear reactor physics and engineering
- Real-time simulation and control systems
- Vacuum and Plasma Arcs
- Gas Dynamics and Kinetic Theory
- Laser Design and Applications
- Laser-Ablation Synthesis of Nanoparticles
- Metal and Thin Film Mechanics
- Particle Dynamics in Fluid Flows
- nanoparticles nucleation surface interactions
- Magneto-Optical Properties and Applications
- Antenna Design and Analysis
Auburn University
2021-2025
University of California, San Diego
2012-2021
Swarthmore College
2019
West Virginia University
2008-2016
Max Planck Institute for Plasma Physics - Greifswald
2016
University of Wisconsin–Madison
2016
Center for Urban Waters
2015
University of Colorado Boulder
2014
Max Planck Institute for Plasma Physics
2012
CEA Cadarache
2012
We present the first experimental observations of dust acoustic wave where was observed to propagate in directions gravity and magnetic field when these were not aligned. The experiments conducted Magnetized Dusty Plasma eXperiment facility using a novel electrode system that allows for angle between be varied controlled way. This letter reports on measurements an rf glow discharge argon plasma environment direction is 45 $^{\circ }$ . When there no applied field, gravity. However, as...
Experiments on HL-2A, DIII-D and EAST show that turbulence just inside the last closed flux surface (LCFS) acts to reinforce existing sheared ExB flows in this region.This flow drive gets stronger as heating power is increased L-mode, leads development of a strong oscillating shear which can transition into H-mode regime when rate energy transfer from exceeds threshold.These effects become compressed time during an L-H transition, but key role turbulent still observed.The results compare...
In dusty plasma environments, spontaneous growth of nanoparticles from reactive gases has been extensively studied for over three decades, primarily focusing on hydrocarbons and silicate particles. Here, we introduce the titanium dioxide, a wide bandgap semiconductor, as nanoparticles. The resultant particles exhibited spherical morphology reached maximum monodisperse radius 235 ± 20 nm after growing 70 s. particle grew linearly, displayed cyclic behavior; that is, upon reaching their...
The kinetic energy transfer between shear flows and the ambient turbulence is investigated in Experimental Advanced Superconducting Tokamak during L-H transition. As rate of from into flow becomes comparable to input turbulence, transition H-mode occurs. observed behavior exhibits several predicted features zonal flows, results show key role that play mediating H-mode.
The absolute rate of nonlinear energy transfer among broadband turbulence, low-frequency zonal flows (ZFs) and geodesic acoustic modes (GAMs) was measured for the first time in fusion-grade plasmas using two independent methods across a range heating powers. results show that turbulent kinetic from intermediate frequencies (20--80 kHz) transferred into ZFs GAMs, as well fluctuations at higher ($>80\text{ }\text{ }\mathrm{kHz}$). As power increased, turbulence GAMs GAM amplitudes peaked then...
We report experimental studies demonstrating a controlled transition to fully developed broadband turbulence in an argon helicon plasma linear device. show the detailed dynamics during from nonlinearly coupled but distinct eigenmodes at low magnetic fields larger fields. As field (B) is increased B ∼ 40 mT, initially we observe slow smooth changes of system (to 140 mT), followed by sharp (within ∼10 mT) centrally peaked narrow density profiles, strong edge potential gradients and pronounced...
In the presence of gravity, micron-sized charged dust particles in a complex (dusty) plasma are compressed into thin layers. However, under microgravity conditions Plasma Kristall-4 (PK-4) experiment on International Space Station (ISS), fill plasma, allowing us to investigate properties three-dimensional (3D) multi-particle system. This paper examines change spatial ordering and thermal state particle system created when stopped by periodic oscillations electric field, known as polarity...
MagNetUS is a network of scientists and research groups that coordinates advocates for fundamental magnetized plasma in the USA. Its primary goal to bring together broad community researchers experimental numerical tools they use order facilitate sharing ideas, resources common tasks. Discussed here are motivation goals this details its formation, history structure. An overview associated facilities projects provided, along with examples scientific topics investigated therein. Finally,...
Helicon plasmas are typically associated with a core, radially localized central area of strong ion light emission. Here, we investigate the role electrostatic instabilities that lead to formation classic blue core. We show helicon plasma can also occur without distinct In these conditions, is dominated by low-frequency resistive drift wave (RDW) propagating in electron diamagnetic direction. When intense sharp core present, new global equilibrium state achieved where three separated exist...
Abstract Although many analytical wellbore heat loss models have been presented, none has addressed the problems associated with (i) directional wells and (ii) changing injection conditions. Today, more are drilled directionally. Moreover, rate, pressure, temperature steam quality seldom remain constant throughout period. This paper presents a semi-analytical model which can determine losses from (deviated or horizontal wells) under To wells, well is divided into number of segments whose...
The transition to drift-interchange turbulence is investigated by estimating the nonlinear spectral power transfer functions of density and potential fluctuations representative for behavior polarization E × B drift nonlinearities using magnetic field strength as control parameter. As parameter increases system undergoes several changes from a quasi-periodic phase locked weakly turbulent regime. nonlinearity transfers kinetic energy larger scales. provides access free coupling at smaller...
The turbulent spatial redistribution of and mean kinetic energy its exchange is investigated in the framework an K-ε model a magnetized plasma column. transferred from turbulence into zonal flow around shear layer. Reynolds stress profile adjusts to layer, which results transport region layer
Using laser induced fluorescence (LIF), radial profiles of azimuthal ion fluid velocity and temperature are measured in the controlled shear de-correlation experiment (CSDX) linear helicon plasma device. Ion velocities temperatures derived from Doppler broadened distribution functions argon ions. The LIF system employs a portable, high power (>300 mW), narrowband (∼1 MHz) tunable diode laser-based operating at 668.614 nm. Previous studies CSDX have shown existence radially sheared...
For drift wave turbulence, due to charge conservation, the divergence of parallel current is coupled perpendicular polarization current, which determines effective radial momentum flux, i.e., Reynolds stress. Changes in flow patterns also affect nonlinear energy transfer from smaller larger scales. Here, we show that by changing end plate boundary conditions a cylindrical plasma device, currents through and hence net transport coupling for inverse are strongly modified. The transition...
We report the observation of a transport bifurcation that occurs by spontaneous self-organization drift-wave and shear flow system in linear plasma device. As we increase magnetic field above threshold (BCr = 1200 G), global transition occurs, with steepening mean density ion pressure profiles, onset strong E×B shearing, reduction turbulence, improved turbulent radial particle transport. An abrupt appears graph flux versus gradient. Hysteresis gradient further confirms this bifurcation. The...
Abstract Radio-frequency (RF) driven helicon plasma sources can produce relatively high-density plasmas ( n > 10 19 m −3 ) at moderate powers (<2 kW) in argon. However, to similar for fusion relevant gases such as hydrogen (H), deuterium (D) and helium (He), much higher RF are needed. For very high powers, thermal issues of the RF-transparent dielectric window, used source design, limit operation timescales. To mitigate this constraint, we have designed, built tested a novel assembly...
Observations in steady-state plasmas confirm predictions that formation of a current-free double layer plasma expanding into chamber larger diameter is accompanied by an increase ionization upstream the layer. The density increases sharply at same driving frequency which appears. For frequencies no appears, large electrostatic instabilities are observed. Time-resolved measurements pulsed discharges indicate initially forms for all frequencies. However, particularly strong layers, appear...
Spectral properties of coherent waves in an argon plasma column are examined using fluctuation data from fast imaging. Visible light ArII line emission is collected at high frame rates a high-speed digital camera. A cross-spectral phase technique allows direct visualization dominant structures as function frequency, well identification azimuthal asymmetries present the system. Experimental dispersion estimates constructed imaging alone. Drift-like identified by comparison with theoretical...
This paper presents an overview of experimental results a laser-produced plasma expanding into background gas, immersed within large range highly uniform magnetic fields (of up to 3 T), that are transverse the plasma. We used intensified gated imaging capture expansion across and along field lines observe spatiotemporal dynamics for different strengths. changes in perpendicular parallel plasmas at high field. In addition, our have also indicated presence electron-ion hybrid instabilities...
We report observations that confirm a theoretical prediction formation of current-free double layer in plasma expanding into chamber larger diameter is accompanied by an increase ionization upstream the layer. The model argues increased needed to balance difference diffusive losses and downstream expansion region. In our helicon source experiments, we find density increases sharply at same antenna frequency which appears.
Time delay estimation (TDE) techniques are frequently used to estimate the flow velocity from fluctuating measurements. Tilted structures carried by lead misinterpretation of time delays in terms direction and amplitude. It affects TDE measurements probes, is also intrinsically important for beam emission spectroscopy gas puff imaging Local eddy shapes estimated 2D field necessary gain a more accurate TDE, as illustrated Langmuir probe array A least square regression approach proposed both...
Using fast-camera measurements the generation mechanism of plasma blobs is investigated in linear device CSDX. During ejection dominated by an $m=1$ mode, which a counterrotating vortex pair. These flows are known to be subject cooperative elliptic instability, characterized disturbance cores and results three-dimensional breakdown two-dimensional flows. The first experimental evidence instability preceding blob-ejection provided terms qualitative evolution geometries internal wave patterns.
The West Virginia University Hot hELIcon eXperiment (HELIX) provides variable density and ion temperature plasmas, with controllable levels of thermal anisotropy, for space relevant laboratory experiments in the Large Experiment on Instabilities Anisotropy (LEIA) as well fundamental studies helicon source physics HELIX. Through auxiliary heating, anisotropy ( T ⊥ / ∥ ) is from 1 to 20 parallel plasma beta (β = 8π nkT i B 2 values that span range 0.0001 0.01 LEIA. velocity distribution...
We report a net inward, up-gradient turbulent particle flux in cylindrical plasma when collisional drift waves generate sufficiently strong sheared azimuthal flow that drives positive (negative) density fluctuations up (down) the background gradient, resulting steepening of mean gradient. The results show existence saturation mechanism for drift-turbulence driven flows can cause transport and profile steepening.